Environmental concerns such as global warming have been a focus of interest and attention in recent years. Under these circumstances, various studies have been conducted on reduction of CO2 emission, and reduction of CO2 concentration in the air by CO2 fixation. For example, active attempts have been made to use biomass, a carbon neutral material, as an energy source alternative to fossil fuels.
Algae are known to produce lipid. If extracted efficiently, the lipid produced by the algae would be an energy source alternative to the fossil fuels. The lipid would also be used as materials for various products. However, cell walls of the algae constitute a major obstacle to the lipid extraction from the algae. The cell walls of the algae are generally hard and flexible, and cannot be disrupted easily. Thus, efficient recovery of the products such as lipid from the algae has been difficult.
For example, Patent Document 1 describes a method of recovering oil-based compounds such as lipid from biomass. According to this method, a biomass suspension with adjusted pH is brought into contact with a nonpolar solvent so that cell products are recovered from the nonpolar solvent and a polar biomass solution.